A thermoplastic injection molding machine typically has a “cold-half” portion that contains appropriately shaped molds, and a matching “hot-half” portion that is connected to an injection system and contains a manifold or the like that provides flow passages for liquefied thermoplastic material to reach the molds in the cold-half. The hot-half of the molding machine contains multiple heaters for heating the injection molding material to maintain it in a liquid phase. To control the heating to maintaining the temperature of the molding material in an optimal range for the molding operation, the temperature in the hot half has to be closely monitored. To that end, thermocouples are typically used for detecting the temperature at different locations in the hot-half. The thermocouples are connected to an external thermocouple controller, which reads the voltage differential between the two wires in each thermocouple as an indication of the temperature at the junction end of the thermocouple wires disposed in the hot-half.
One problem frequently experienced by manufacturers that use injection molding systems is the damages to the thermocouple circuits caused by leakage current from heating elements. The heating elements in a molding machine are typically operated at a high current and relatively high voltage. If a heating element is not properly grounded, the current from that heating element may find its way to a nearby thermocouple wire and use the thermocouple wire as its return path. Such leakage current may destroy the thermocouple wire and damage the thermocouple controller.